3-arylacrylic acid ester light-protection stabilizers for organic material

ABSTRACT

The use of 3-arylacrylic esters I ##STR1## where Ar is an aryl radical which can additionally carry substituents, 
     R 1  is the residue of an n-hydric aliphatic polyol having up to 20 carbon atoms, where the carbon chain can be interrupted by up to 9 non-adjacent oxygen atoms, or of an n-hydric cyclo-aliphatic polyol having 5 to 20 carbon atoms in which ring carbon atoms can also be replaced by non-adjacent oxygen atoms, 
     R 2  and R 3  are hydrogen or C 1  --C 4  -alkyl, and 
     n is a number from l to 10, 
     as stabilizers, in particular against the action of light, for non-living organic material.

BACKGROUND OF THE INVENTION

1. Field Of The Invention

The present invention relates to the use of 3-arylacrylic esters of thegeneral formula I ##STR2## where Ar is an aryl radical which canadditionally carry substituents,

R¹ is the residue of an n-hydric aliphatic polyol having up to 20 carbonatoms, where the carbon chain can be interrupted by up to 9 non-adjacentoxygen atoms, or of an n-hydric cyclo-aliphatic polyol having 5 to 20carbon atoms in which ring carbon atoms can also be replaced bynon-adjacent oxygen atoms,

R² and R³ are hydrogen or C₁ --C₄ -alkyl, and

n is a number from 1 to 10,

as stabilizers, in particular against the action of light, fornon-living organic material.

2. Description Of The Background Art

3-Arylacrylic esters of the abovementioned type, for example2-ethylhexyl p-methoxycinnamate, have been known for a long time incosmetics for protecting the human skin against the action of light.

The compounds used to date to protect non-living organic material, inparticular plastics and surface coatings, have had different chemicalstructures, for example sterically hindered amines of thepolyalkylpiperidine type or benzotriazole derivatives. Agents of thistype are intended to combat the damage to organic material which isnormally manifested by yellowing or discoloration and embrittlement ofthe organic material.

Said prior art agents are frequently still unsatisfactory in that theircompatibility with plastics is too low, the duration of the protectiveeffect is too short, the substances have an intrinsic color and arevolatile, and the stabilizers undergo thermal decomposition onincorporation at elevated temperature.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide stabilizers, inparticular against the action of light, which afford more effectiveprotection for organic material. It was particularly intended toincrease the duration of the protective effect.

We have found that this object is achieved by using the 3-aryl-acrylicesters I defined at the outset.

In a preferred embodiment, Ar is a phenyl, biphenyl sic! or naphthylradical which can be substituted by one to three C₁ --C₄ -alkyl groups,C₁ --C₄ -alkoxy groups, hydroxyl groups, phenoxy groups, amino groupswhich can be mono- or disubstituted by C₁ --C₄ -alkyl groups, or halogenatoms, nitro groups or a methylene-dioxy group, it being possible forthe substituents to be identical or different.

Examples of Ar which may be mentioned are:

phenyl,

o-, m- of p-tolyl,

o-, m- or p-ethylphenyl,

o-, m- or p-propylphenyl,

m- or p-cumyl,

o-, m- or p-butylphenyl,

m- or p-isobutylphenyl,

m- or p-sec-butylphenyl,

m- or p-tert-butylphenyl,

2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-dimethylphenyl,

mesityl,

o-, m- or p-methoxyphenyl,

o-, m- or p-ethoxyphenyl,

o-, m- or p-propoxyphenyl,

m- or p-isopropoxyphenyl,

o-, m- or p-butoxyphenyl,

m- or p-isobutoxyphenyl,

m- or p-sec-butoxyphenyl,

m- or p-tert-butoxyphenyl,

2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-dimethoxyphenyl,

o-, m- or p-hydroxyphenyl,

2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-dihydroxyphenyl,

3-hydroxy-4-methoxyphenyl,

m- or p-phenoxyphenyl,

o-, m- or p-aminophenyl,

o-, m- or p-(N-methylamino)phenyl,

o-, m- or p-(N,N-dimethylamino)phenyl,

o-, m- or p-fluorophenyl,

o-, m- or p-chlorophenyl,

2,4-dichlorophenyl,

o-, m- or p-bromophenyl,

o-, m- or p-nitrophenyl,

2,3- or 3,4-methylenedioxyphenyl,

2-, 3- or 4-biphenyl sic! and

α- or β-naphthyl.

C₁ --C₄ -Alkoxyphenyl radicals are particularly preferred, especiallywhen the alkoxy radical is in the p position on the phenyl nucleus.Among these radicals, attention is drawn particularly top-methyoxyphenyl.

Where n=1, examples of R¹ are the following aliphatic radicals: methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,n-pentyl, isopentyl, sec-pentyl, tert-pentyl, neopentyl, n-hexyl,n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, isononyl, n-decyl, n-undecyl,n-dodecyl, n-tridecyl, isotridecyl, n-tetra-decyl, n-hexadecyl,n-octadecyl, n-eicosyl, vinyl, allyl, methallyl, oleyl, linolyl andlinolenyl. Of these, straight-chain or branched C₅ --C₁₆ -alkyl groups,in particular straight-chain or branched C₈ --C₁₂ -alkyl groups, arepreferred. Straight-chain or branched C₈ -alkyl groups including, inparticular, 2-ethylhexyl are of particular interest.

where n=2 to 10, suitable examples of n-valent radicals R¹ derived frompolyols of the formula R¹ (OH)_(n) are, in particular, those which have2 to 12 carbon atoms and which can be interrupted in their linear orbranched carbon framework by up to 3 non-adjacent oxygen atoms or whichcan contain individual oxygen atoms in their cyclic carbon framework. Afew examples thereof are: ##STR3##

Examples of suitable polyvalent cycloaliphatic radicals are those whichare derived from the polyhydric alcohols 1,3-cyclopentanediol,1,3-cyclohexanediol or, particularly, from 1,4-cyclohexanediol or1,4-cyclohexanedimethanol, it also being possible for the cycloalkylrings to be substituted by further alkyl groups.

The variable n is preferably a number from 1 to 6, in particular from 1to 4, but especially 1 or 2.

The radicals R² and R³ are, independently of one another, in particularhydrogen, methyl or ethyl. Compounds I where R² is hydrogen or methyland R³ is hydrogen are very particularly preferred.

The 3-arylacrylic esters I are outstandingly suitable for stabilizingnon-living organic material against the action of light, oxygen andheat. They are also effective as metal deactivators. They are added tothe organic material to be stabilized in a concentration of from 0.01 to5%, preferably from 0.02 to 2%, of the weight of the organic material,before, during or after its production.

Non-living organic material means, for example, cosmetic products suchas ointments and lotions, pharmaceutical formulations such as pills andsuppositories, photographic recording materials, especially photographicemulsions, or precursors for plastics and surface coatings, butespecially plastics and surface coatings themselves.

The present invention also relates to non-living organic materialstabilized against the action of light, oxygen and heat, especiallyplastics and surface coatings, which contains one or more compounds I inthe abovementioned concentrations.

The compounds I can be mixed in particular with plastics using all knownequipment and methods for mixing stabilizers or other additives intopolymers.

The non-living organic material stabilized by the compounds I may alsocontain further additives, eg. antioxidants, light stabilizers, metaldeactivators, antistatic agents, flame retardants, pigments and fillers.

Antioxidants and light stabilizers which can be added beside thecompounds I are, for example, compounds based on sterically hinderedphenols, sterically hindered amines, chroman derivatives or sulfur- orphosphorus-containing costabilizers.

Examples of phenolic antioxidants which may be mentioned are2,6-di-tert-butyl-4-methylphenol, n-octadecylβ-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate,1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl) butane,1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl)benzene,1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, 1,3,5-trisβ-(3,5-di-tert-butyl-4-hydroxybenzyl)propionylethyl! isocyanurate,1,3,5-tris(2,6-dimethyl-3-hydroxy-4-tert-butylbenzyl) isocyanurate andpentaerythritol tetrakis β-3,5-di-tert-butyl-4-hydroxyphenyl)propionate! sic!.

Examples of suitable phosphorus-containing antioxidants aretris(nonylphenyl) phosphite, distearyl pentaerythritol diphosphite,tris(2,4-di-tert-butylphenyl) phosphite, distearyl pentaerythritoldiphosphite sic!, tris(2-tert-butyl-4-methylphenyl) phosphite,bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite andtetrakis(2,4-di-tert-butylphenyl) 4,4'-biphenylene diphosphite.

Examples of sulfur-containing antioxidants which may be mentioned aredilauryl thiodipropionate, dimyristyl thiodipropionate, distearylthiodipropionate, pentaerythritol tetrakis-β-laurylthiopropionate) sic!and pentaerythritol tetrakis(-β-hexylthiopropionate). It is furthermorepossible to add thiobisphenols such as3,3'-di-tert-butyl-4,4'-dihydroxy-2,2'-dimethyldiphenyl sulfide.

Examples of further antioxidants and light stabilizers which can be usedtogether with the compounds I are 2-(2-hydroxyphenyl)-benzotriazoles,2-hydroxybenzophenones, aryl esters of hydroxybenzoic acids,α-cyanocinnamic acid derivatives, benzimidazole-carboxanilides, nickelcompounds or oxanilides.

Particularly effective stabilization is obtained when at least One otherlight stabilizer from the class of sterically hindered amines is addedin the usual concentration in addition to compounds I.

Examples of further sterically hindered amines suitable for this purposeare: bis(2,2,6,6-tetramethylpiperidyl) sebacate,bis(1,2,2,6,6-pentamethylpiperidyl) sebacate, the condensate of1-hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxypiperidine with succinicacid, the condensate of N,N'-(2,2,6,6-tetramethylpiperidyl)hexamethylenediamine with4-tert-octylamino-2,6-di-chloro-1,3,5-triazine,tris(2,2,6,6-tetramethylpiperidyl) nitrilotriacetate,tetrakis(2,2,6,6-tetramethy-4-piperidyl)-1,2,3,4-butanetetracarboxylicacid sic!, 1,11-(1,2-ethanediyl)-bis (3,3,5,5-tetramethylpiperazinone),and the condensates of 4-amino-2,2,6,6-tetramethylpiperidines withtetramethylolacetylenediureas.

Particularly effective stabilization of polyurethanes is obtained when asterically hindered amine, eg. bis(2,2,6,6-tetramethylpiperidyl)sebacate or bis(1,2,2,6,6-pentamethylpiperidyl) sebacate and, inaddition, a mixture of a chroman derivative (vitamin E, α-tocopherol),an organic phosphate and an amine as described in German PatentApplication P 44 05 670.2 are added, in the usual concentration, inaddition to the compounds I.

A mixture of the compounds I with a sterically hindered amine and achroman derivative is also suitable and particularly advantageous forstabilizing plastics, especially polyurethanes.

Examples of plastics and thermosets which can be stabilized by thecompounds I are:

polymers of mono- and diolefins such as low- and high-densitypolyethylene, polypropylene, linear poly-1-butene, polyisoprene,polybutadiene, and copolymers of mono- or diolefins or mixtures of saidpolymers;

copolymers of mono- or diolefins with other vinyl monomers such asethylene/alkyl acrylate copolymers, ethylene/alkyl methacrylatecopolymers, ethylene/vinyl acetate copolymers or ethylene/ acrylic acidcopolymers;

polystyrene and copolymers of styrene or α-methylstyrene with dienesand/or acrylic derivatives such as styrene/butadiene,styrene/acrylonitrile (SAN), styrene/ethyl methacrylate, styrene/butadiene/ethyl acrylate, styrene/acrylonitrile/methacrylate,

acrylonitrile/butadiene/styrene (ABS) or methyl methacrylate/butadiene/styrene (MBS);

halogenated polymers such as polyvinyl chloride, polyvinyl fluoride,polyvinylidene fluoride and copolymers thereof; polymers derived fromα,β unsaturated acids and derivatives thereof, such as polyacrylates,polymethacrylates, polyacrylamides and polyacrylonitriles;

polymers derived from unsaturated alcohols and amines or their acrylicderivatives or acetals, eg. polyvinyl alcohol and polyvinyl acetate;

polyurethanes, polyamides, polyureas, polyphenylene ethers, polyesters,polycarbonates, polyoxymethylenes, polysulfones, polyether sulfones andpolyether ketones.

It is furthermore possible to stabilize surface coatings with thecompounds I, eg. industrial coatings. Among these, particular emphasisis placed on stoved coatings, and among these in turn on automotivecoatings, preferably two-layer coatings.

The compounds I can be added in solid or dissolved form to the coatingagent. Their good solubility in coating systems is a particularadvantage in this connection.

The compounds I are preferably used to stabilize polyurethanes,especially polyurethane foams, but also polyurethane moldings,polycarbonates and automotive coatings, especially in the automobilesector.

The compounds I are distinguished by being very compatible withconventional types of plastic and having good solubility and excellentcompatibility in conventional coating systems. They are stable andnonvolatile at conventional plastic- and surface coating-processingtemperatures. Particular advantages which may be emphasized over knownstabilizers are that the compounds I to be used according to theinvention have distinctly less intrinsic color and thus have virtuallyno effect on the neutral shade of, especially, transparent plastics suchas polycarbonates, polymethylmethacrylate and polyesters, polyurethanefoams and surface coatings. In addition, the compounds I used accordingto the invention have an improved stabilizing effect, ie. in theirpresence the material begins to deteriorate much later.

EXAMPLES OF USE EXAMPLE 1

(Polycarbonate)

0.20 part by weight of 2-ethylhexyl p-methoxycinnamate (A) wasincorporated into 100 parts by weight of polycarbonate (Macrolon®PC 2800from Bayer) by a single extrusion at 280° C., and the resulting granuleswere converted into test specimens 2 mm thick in an injection moldingmachine at 300° C.

The test specimens produced in this way were tested for their light- andweather-resistance in a Xenotest® 1200 accelerated weathering machine.The aging was determined by measuring the ASTM D 1925 yellowness indexafter defined time intervals. The illumination time did not exceed 2,000hours in any of the tests.

For comparison with the prior art, the benzotriazole derivative of theformula B was incorporated in the same way in the same amounts into thesame polycarbonate and tested in the same way. ##STR4## The results arecompiled in Table

                  TABLE 1                                                         ______________________________________                                                Yellowness index after hours (Xenotest 1200)                          Stabilizer                                                                              0         1000      1500    2000                                    ______________________________________                                        No stabilizer                                                                           10.3      15.5      20.1    21.8                                    A (according to                                                                         10.2      11.0      14.2    15.3                                    the invention)                                                                B (comparative)                                                                         11.5      12.7      15.6    16.8                                    ______________________________________                                    

EXAMPLE 2

(Polyurethane Foam)

(Preparation Of The Illumination Samples):

A polyol component comprising 41.9 g of a polyetherol (OH number: 29.0)which had been obtained by addition of propylene oxide and ethyleneoxide onto propylene glycol and contained approximately 84% by weightprimary hydroxyl groups, 42.5 g of a polyetherol (OH number: 27.0) whichhad been obtained by addition of propylene oxide and ethylene oxide ontotrimethylolpropane and contained approximately 88% by weight primaryhydroxyl groups, 8.1 g of 1,4-butanediol, 1.724 g of a 25% by weightsolution of diazabicyclooctane in 1,4-butanediol, 0.016 g of dibutyltindilaurate, 0.1 g of the silicone stabilizer OS 710 from Bayer, 5.49 g offluorotrichloromethane and 0.17 ml of water were mixed with thestabilizers specified below (0.5 g of each) and foamed to test sheets inthe ratio of 100:48.5 by weight with a prepolymer which had 23.0% byweight isocyanate groups at 25° C. (component and tool temperature). TheNCO prepolymer in this case had been prepared from 87.17 g of4,41-diphenylmethane diisocyanate, 4.83 g of a polyetherol (OH number:250) which was obtained by addition of propylene oxide onto propyleneglycol, and 8.0 g of dipropylene glycol.

The compound used according to the invention was compound A fromExample 1. Compound C obtained from the two stated components was usedfor comparison with the prior art. ##STR5##

The test sheets were illuminated in a Xenotest 450 and then the ASTM D1925 yellowness index was determined. The results are shown in Table

                  TABLE 2                                                         ______________________________________                                                   Yellowness index after hours (Xenotest 450)                        Stabilizer   0             240                                                ______________________________________                                        No stabilizer                                                                              2.8           45.2                                               A (according to the                                                                        3.0           17.0                                               invention)                                                                    C (comparative)                                                                            3.4           18.4                                               ______________________________________                                    

EXAMPLE 3

0.5% by weight of the compound ##STR6## were dissolved together with 0.5% by weight of N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-N,N'-bisformyl-1,6-diaminohexane byextrusion once in white acrylonitrile/butadiene/styrene copolymer (ABS)at 250° C. (based on the total amount of copolymer). The resultinggranules were injection molded at 260° C. to give articles 2 mm thick.The moldings were examined for their lightfastness in an acceleratedlight-exposure instrument (Xenotest 450 type). The yellowing caused byphotooxidative degradation of the polymer was measured. The yellowingwas expressed by the yellowness index YI determined in accordance withUS standard ASTM D 1925. A high index means severe yellowing.

In parallel with the example compounds, the known UV absorber ethyl2-cyano-3,3-diphenylacrylate was incorporated as comparative example inthe same concentration together with the sterically hindered piperidinein ABS. Table 3 shows the yellowing behavior of the example compoundcompared with the UV absorber used in a known manner.

EXAMPLE 4

0.5% by weight of the compound ##STR7## were extruded together with 0.5%by weight ofN,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-N,N'-bisformyl-1,6-diaminohexanein ABS and investigated in an accelerated light-exposure test as inExample 3. The result is shown in Table 3.

                  TABLE 3                                                         ______________________________________                                                Yellowness index after hours (Xenotest 450)                           Stabilizer                                                                              0 hours   1000 hours                                                                              400 hours at 90° C.                      ______________________________________                                        Comparative                                                                             18.5      21.0      30.0                                            example                                                                       Example 3 19.0      19.7      29.8                                            Example 4 18.9      19.5      26.9                                            ______________________________________                                    

We claim:
 1. A method of stabilizing a polyurethane polymer comprisingcombining said polyurethane with at least one 3-arylacrylic ester of theformula I: ##STR8## where Ar is an aryl radical, optionaliy substitutedby one to three C₁ -C₄ -alkyl groups, C₁ -C₄ -alkoxy groups, hydroxylgroups, phenoxy groups, amino groups which can be mono- or disubstitutedby C₁ -C₄ -alkyl groups, or halogen atoms, nitro groups or amethylenedioxy group, said substituents being identical or different,R¹is the residue of an n-hydric aliphatic mono- or polyol having, up to 20carbon atoms, where the carbon chain can be interrupted by up to 9non-adjacent ether oxygen atoms, or of an n-hydric cyclo-aliphaticpolyol having 5 to 20 carbon atoms in which ring carbon atoms can alsobe replaced by non-adjacent ether oxygen atoms, R² and R³ are each,independently, hydrogen or C₁ -C₄ -alkyl, and n is a number from 1 to10.
 2. The method as claimed in claim 1, where Ar is a C₁ --C₄-alkoxyphenyl radical.
 3. The method as claimed in claim 1, where Ar isp-methoxyphenyl.
 4. The method as claimed in claim 1, where R¹ is theresidue of a straight-chain or branched aliphatic polyol having 5 to 16carbon atoms.
 5. The method as claimed in claim 1, wherein n is 1 and R¹is 2-ethylhexyl.
 6. The method as claimed in claim 1, where R² ishydrogen or methyl and R₃ is hydrogen.
 7. The method as claimed in claim1, where n is
 1. 8. The method as claimed in claim 1, wherein saidpolyurethane is coated on a surface to form a coating.
 9. A compositioncomprising:a polyurethane or polycarbonate polymer; and 0.01 to 5% byweight, based on the weight of said organic material, of a 3-arylacrylicester of formula I: ##STR9## where Ar is an aryl radical optionallysubstituted by one to three C₁ --C₄ -alkyl groups, C₁ --C₄ -alkoxygroups, hydroxyl groups, phenoxy groups. amino groups which can be mono-or disubstituted by C₁ --C₄ -alkyl groups, or halogen atoms, nitrogroups or a methylenedioxy group said substituents being identical ordifferent. R¹ is the residue of an n-hydric aliphatic polyol having upto 20 carbon atoms, where the carbon chain can be interrupted by up to 9non-adjacent ether oxygen atoms, or of an n-hydric cyclo-aliphaticpolyol having 5 to 20 carbon atoms in which ring carbon atoms can alsobe replaced by non-adjacent ether oxygen atoms, R² and R³ are eachindependently, hydrogen or C₁ --C₄ -alkyl, and n is a number from 2 to10.
 10. A composition as set forth in claim 9, wherein said polymer is apolyurethane.
 11. A composition as set forth in claim 10, wherein Ar isa C₁ --C₄,-alkoxyphenyl radical.
 12. The composition as set forth inclaim
 11. wherein Ar is p-methoxyphenyl.
 13. The composition as setforth in claim 9, wherein Ar is p-methoxyphenyl, n is 2 and R¹ is adihydric polyol.
 14. The composition of claim 13, wherein the dlhydricpolyol is cyclohexane dimethanol.
 15. A method as set forth in claim 1,wherein said polyurethane/stabilizer combination is formed into a foam.16. The composition of claim 13, wherein the dihydric polyol is1,4-butanediol.
 17. A composition comprising:a polyurethane orpolycarbonate polymer; and 0.01 to 5% by weight, based on the weight ofsaid organic material, of a 3-arylacrylic ester of formula I: ##STR10##where Ar is an aryl radical optionally substituted by one to three C₁--C₄ -alkyl groups C₁ --C₄ -alkoxy groups, hydroxyl groups phenoxygroups, amino groups which can be mono- or disubstituted by C₁ --C₄-alkyl groups, or halogen atoms, nitro groups or a methylenedioxy group,said substituents being identical or different, R¹ is the residue of ann-hydric aliphatic polyol having, up to 20 carbon atoms, where thecarbon chain can be interrupted by up to 9 non-adjacent ether oxygenatoms, or of an n-hydric cyclo-aliphatic polyol having 5 to 20 carbonatoms in which ring carbon atoms can also be replaced by non-adjacentether oxygen atoms, R ² and R³ are each independently, hydrogen or C₁--C₄ -alkyl, and n is a number from 2 to 10.